Abstract

The aim of this research was to identify the abutment-implant gap using 20 N or 30 N torques for the abutment. A descriptive study was designed using 3 internal hex implant systems from four different companies; the implants were manipulated in a usual way, installing the respective prosthetic abutment in each platform using 20 N/cm2 and 30 N/cm2 torque. Then, observations were made and photos taken a LEO 1420 VP scanning electron microscope; the data were analyzed with the Shapiro-Wilk test of normality and t-test for related samples, considering a value of p<0.05 for significant differences to compare the group with 20N and the group with 30N torque. Significant differences were identified between the gap in abutments installed with either 20 N/cm2 or 30 N/cm2, with fewer differences being observed in the latter group. There were wide variations between the study units, with reductions from 49% to 23% from the interface with the lower (20 N/cm2) to the higher torque (30 N/cm2). It can be concluded that the installation torque of prosthetic abutments influences the interface between prosthetic connector and implant surface.

Keywords

Implant gap, Abutment, Dental implant

Introduction

The gap between the abutment and the platform is relevant to
the short and long-term results in different types of implant
restoration. Bacterial colonization of the implant surface leads
to inflammatory changes that can be reversible in soft tissues;
when the phenomenon reaches bone level a well-known
disease like peri-implantitis occurs [1,2]. It has been shown
that in the connection between abutment and implant the
bacteria can find a place that allows their mobility until them
reaching the implant bed [3], which could cause significant
complications. Adjustment defects between abutment and
implant added to the lack of passive adaptation between the
prosthesis and the implant can promote the fracture of the
prosthetic screw [4] and produce other types of complications.

Discrepancies in fit and spaces between components are
inevitable when two different parts are positioned [5];
therefore, efforts have been made to maximize the fit of the
connections between implant and abutment. Some studies have
determined the measurement of these interface spaces using
electron microscopy [6], and a standard marginal space
measurement of 45 μm has been proposed. Other studies have
measured spaces smaller than 12 μm, whereas others have
reported average values of microspaces from 2.3 to 5.6 μm [2].

The aim of this study is to identify the space between the
prosthetic abutment and implant platform in four different
brands (with internal hex connection) frequently found on the
international market.

Materials and Methods

A descriptive study was designed to analyze the gap between
abutment and platform of implant using two different
installation torques. To do this, 3 implant units from 4 brands
were used (Table 1) that fulfilled the study conditions of an
internal hex and standardization. For the analyses, the implants
and their components were acquired in the formal market
through their conventional form of sale. All the implants were
removed from their packages with specific tweezers and
implant mount, limiting any contact at platform level and the
places to be used in the measurements.

Company

Implant

Measurements

Medigma

Fix tite

3.75 × 13

Biohorizons

Tapered internal

3.8 × 12

Alpha Bio

Atid

3.75 × 13

B & W

Cónico CIH

4.0 × 13

Table 1: Distribution of the 4 types of implants and commercial
brands used to applied the 20N and 30N torque in the abutment.

For the implants, the abutments installed were used with
progressive torques in 9 different configurations, reaching two
final installation torques: 20 N/cm2 (group 1 with 12 implants)
and 30 N/cm2 (group 2 with 12 implants). For this phase, each
implant was held firm in a pressure system that rendered the
implants immobile. Once torque was applied to the abutments,
the implants were installed in a wax-based cubical system that kept the system stable and subjected to observation and
photography using a scanning electron microscope (SEM, LEO
1420 VP), using acceleration values and focal length according
to the magnification used in the image (50X, 500X, 1000X).

Given the variability observed on the surfaces of metallic
structures, a specific point was determined to take the
measurement (the selected point had to be repeatable and
easily identifiable, determining from 1 mm inwards from the
outer edge of the platform), making it possible to standardize
the comparison.

The measurements were taken by qualified personnel with
experience in the use of this SEM system; each unit was
measured individually, recording its values in a table designed
specifically for the study. The data were analyzed with
measures of central tendency and a statistical analysis with the
Shapiro-Wilk test of normality and t-test for related samples,
making a comparison between 12 units with 20 N torque
(group 1) vs. 12 units with 30N torque (group 2). The data
were analyzed with the SPSS/PC + v. 20.0 software (SPSS,
Chicago, USA), considering a value of p<0.05 for significant
differences.

Results

The tests were applied without complications. The results
showed a significant relation between the torque applied to the
abutment and the gap in the abutment-implant interface
(p<0.05) when the group 1 and group 2 were analyzed (Table
2). The gaps were variable. The surface of each implant also
presented different variations and morphologies (Figures 1-4).

Company

Gap between abutment and implant platform (nm)

Difference between averages

20 N/cm2

30 N/cm2

X (nm)

SD

X (nm)

DE

A

317.6

95.1

209

54.51

108.6

B

404.5

243.8

231.1

29.21

173.4

C

244.5

26.3

125.3

27.1

119.2

D

280.1

31.1

215.9

14.14

64.2

Average

311.7

99.1

195.3

31.2

116.4

Table 2: Gaps obtained for each implant system according to their
brand, doing a comparative analysis using 12 implants in each group.

For each implant system analyzed clear differences were
observed in the gap when 20 N/cm2 and 30 N/cm2 were
compared. Brand D had the fewest differences in the existing
spaces, whereas brand B had the greatest variation. It was not
possible to obtain statistical relations between the brands due
to the small number of samples used.

From a percentage point of view, the gap reduction in the
interface was observed in group A with 35%, group B with
43%, group C with 49% and group D with 23%, showing the
impact of 10-Ncm torque on the abutment installation.

Discussion

Scanning electron microscopy enables a microstructural
analysis to identify the actual condition of different metal
systems. This technology has been applied previously to
identify implant surfaces as well as variations in systems, both
in design and connection, which involves studies of fit and
irregularities in the manufacture [7].

King [8] used periapical x-rays to study the bone response of
implants installed in terms of load, finding different interface
sizes, which apparently had no influence on bone crest
migration. Vidigal [9] reported results with interface variations
between 20 and 150 μm, which show a broad variation and
chances for bacterial contamination. Rodriguez and Baena [10]
also indicated that surface type might be related to the
migration and presence of microorganisms through the
interface.

Nakazato [11] and Koha [12], independently, conducted studies
where they confirmed that 14 days after the insertion of the
prosthetic abutment on the implant, the interface was already
being colonized by common bacteria in the mouth,
demonstrating the importance of recognizing and reducing this
interface in implant systems. The normal conditions of the oral
environment allow these microbial migrations to develop more
frequently; however, Jansen [2] found no significant relations
between the interface size and bacterial contamination.

The corrosion related to a poor fit is another condition that
must be assessed. De Oliveira [13] performed these in vitro
analyses, observing that the increase in corrosion could lead to
a fracture of metal systems, causing major complications in a
clinical environment. The size of the space between abutment
and platform could be a variable in the presence of corrosion.

In our results, it is worthy of note that only two of the four
brands evaluated indicate an installation torque for the
prosthetic abutment as formal manufacturer’s instructions,
whereas the other two do not mention it. Our results confirm
previous studies where the highest torque to insert the
abutment affects the reduction of the abutment- implant
platform interface. Another interesting observation from our
results lies in the wide variability among the brands; however,
given the small sample number, statistical comparisons are not
possible. Nevertheless, it does allow speculation regarding the guarantee that these systems offer in medium and long-term
implant restoration.

The size of the bacteria is smaller than the implant-connector
interface [14], so that larger spaces allow large bacterial
invasions. There are several factors, however, that influence
the presence of these interfaces; therefore, the abutment
insertion torque could be highly relevant to reducing the space
in the connection. May be more important than the connection
itself given that de Oliveira [15] did not any observe significant
differences when they compared the interface spaces in internal
hex and external hex implants, even though the internal
connection had smaller interfaces. Jaworski [16] also found
that Morse taper systems had fewer interface spaces than other
implant systems. In the present study, internal connection
systems were selected exclusively as they are more frequently
used in the market and there is a variety of internal
connections.

Conclusion

It may be concluded that the amount of torque to insert the
abutment on the implant platform significantly influences the
size of the interface, decreasing when the torque is greater.